For manually applied Gas Tungsten Arc Welding (GTAW), which is the most widely selected welding process for aerospace related hardware, the filler metal is added into the molten weld pool in the form of wire which may be any of a variety of diameters from as small as 1/64" to as large as 3/16". Adding the wire is performed by the welder manually with one hand while the welding torch (arc heat source) is held and manipulated at the target weld location with the other hand. The action of manually manipulating the filler wire is a skill requiring significant physical dexterity in the hand, finger and wrist movements as well as precise mental dexterity regarding hand-to-eye coordination.
To ensure weld consistency, and thus weld integrity and resultant high quality hardware, the filler wire must be fed into the molten weld pool in a selective and specific manner to work in unison with the manual manipulations of the weld torch, which is applied and controlled by the opposite hand. Wide variations in specific hand, wrist, and finger movements are used from one welder to the next. No one specific hand technique/motion has been found which suits the skill level of every welder. Because of this, the repeatability and reliability of the GTAW process, when manually applied, is highly dependent upon the human factor; that is, the skill of the welder in manipulating the welding torch while concurrently feeding the filler wire into the weld pool.
Various welding wire feed systems are available in the prior art. For example, U.S. Pat. No. 5,155,832 discloses a welding wire feeder designed to fit in a user's hand. A thumb operated feed wheel rolls against an idler roller and frictionally advances the welding wire through the rollers and a pair of guide tubes.
U.S. Pat. No. 4,206,862 discloses a device including an electric motor for advancing welding wire through a handpiece. A potentiometer responsive to a finger pressure-sensitive switch on the handpiece regulates the motor speed and rate of wire advancement.
U.S. Pat. No. 1,377,792 discloses a tube to hold welding wire with a finger-operated friction lock to fix the wire in the tube until more wire is desired at which time the wire is simply grasped and slid further into the tube.
U.S. Pat. No. 3,989,697 discloses a wire feeder device for mounting on the welder's hand between the thumb and index finder. The wire is passed through fixed and moveable tubular feeders on the device which are designed to advance the wire as the moveable feeder moves back and forth when the index finger and thumb are squeezed together and released.
U.S. Pat. No. 5,782,394 disclosed a manual hand-held wire feeder having a tubular holder through which the welding wire is passed. The feeder includes a finger wheel on the holder and an idler wheel biased to the finger wheel by an elastic band. The wire is advanced by the finger wheel which is rotated by the index finger.
U.S. Pat. No. 5,584,426 discloses a welding wire holding device comprising a housing with a handle. The wire is passed through the housing and advanced by a thumb wheel mounted within the housing but protruding from the side thereof so as to allow its manipulation by the welder's thumb whereby the wire is advanced between a driving roller and compression roller.
All of the foregoing have disadvantages in one aspect or another in that they are structurally complex, unduly large, heavy and expensive, may require considerable efforts and dexterity of the welder in using the feeder device and in loading welding wire thereon, and with an associated and undesirable expenditure of time.